TGF-β/Smad signaling inhibits the activity of the AFP promoter together with ATBF1. (a) Schematic presentation of deletion mutants of the AFP promoter. between −4120 and −3756 and between −3492 and −3300 are enhancer elements. between −1807 and −1725 and between −317 and −300 are silencer elements. P indicates a promoter. (b) Effect of TGF-β on the activity of the AFP promoter. The examined luciferase reporters (500 ng) were transfected into HepG2 cells. The cells were then stimulated with 5 ng/mL TGF-β. (c) Cooperation of ATBF1 with the TGF-β signaling for suppression of the activity of the AFP promoter. ATBF1 expression plasmid (200 ng) was transfected into HepG2 cells with Δ2.7Luc (500 ng). The cells were then stimulated with 5 ng/mL TGF-β. (d) Effect of Smads and ATBF1 on the transcriptional activity of Δ2.7Luc. HepG2 cells were transfected with Smads (100 ng), ATBF1 (200 ng), or their combination together with Δ2.7Luc (500 ng). The cells were then stimulated with 5 ng/mL TGF-β.